// Copyright (c) 2008, Fair Oaks Labs, Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//  * Redistributions of source code must retain the above copyright notice,
//    this list of conditions and the following disclaimer.
//
//  * Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//
//  * Neither the name of Fair Oaks Labs, Inc. nor the names of its contributors
//    may be used to endorse or promote products derived from this software
//    without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
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//
// Modifications to writeIEEE754 to support negative zeroes made by Brian White

// ref: https://github.com/nodejs/node/blob/87286cc7371886d9856edf424785aaa890ba05a9/lib/buffer_ieee754.js

exports.read = function readIEEE754(buffer, offset, isBE, mLen, nBytes) {
    var e, m,
        eLen = nBytes * 8 - mLen - 1,
        eMax = (1 << eLen) - 1,
        eBias = eMax >> 1,
        nBits = -7,
        i = isBE ? 0 : (nBytes - 1),
        d = isBE ? 1 : -1,
        s = buffer[offset + i];

    i += d;

    e = s & ((1 << (-nBits)) - 1);
    s >>= (-nBits);
    nBits += eLen;
    for (; nBits > 0; e = e * 256 + buffer[offset + i], i += d, nBits -= 8);

    m = e & ((1 << (-nBits)) - 1);
    e >>= (-nBits);
    nBits += mLen;
    for (; nBits > 0; m = m * 256 + buffer[offset + i], i += d, nBits -= 8);

    if (e === 0) {
        e = 1 - eBias;
    } else if (e === eMax) {
        return m ? NaN : ((s ? -1 : 1) * Infinity);
    } else {
        m = m + Math.pow(2, mLen);
        e = e - eBias;
    }
    return (s ? -1 : 1) * m * Math.pow(2, e - mLen);
};

exports.write = function writeIEEE754(buffer, value, offset, isBE, mLen, nBytes) {
    var e, m, c,
        eLen = nBytes * 8 - mLen - 1,
        eMax = (1 << eLen) - 1,
        eBias = eMax >> 1,
        rt = (mLen === 23 ? Math.pow(2, -24) - Math.pow(2, -77) : 0),
        i = isBE ? (nBytes - 1) : 0,
        d = isBE ? -1 : 1,
        s = value < 0 || (value === 0 && 1 / value < 0) ? 1 : 0;

    value = Math.abs(value);

    if (isNaN(value) || value === Infinity) {
        m = isNaN(value) ? 1 : 0;
        e = eMax;
    } else {
        e = Math.floor(Math.log(value) / Math.LN2);
        if (value * (c = Math.pow(2, -e)) < 1) {
            e--;
            c *= 2;
        }
        if (e + eBias >= 1) {
            value += rt / c;
        } else {
            value += rt * Math.pow(2, 1 - eBias);
        }
        if (value * c >= 2) {
            e++;
            c /= 2;
        }

        if (e + eBias >= eMax) {
            m = 0;
            e = eMax;
        } else if (e + eBias >= 1) {
            m = (value * c - 1) * Math.pow(2, mLen);
            e = e + eBias;
        } else {
            m = value * Math.pow(2, eBias - 1) * Math.pow(2, mLen);
            e = 0;
        }
    }

    for (; mLen >= 8; buffer[offset + i] = m & 0xff, i += d, m /= 256, mLen -= 8);

    e = (e << mLen) | m;
    eLen += mLen;
    for (; eLen > 0; buffer[offset + i] = e & 0xff, i += d, e /= 256, eLen -= 8);

    buffer[offset + i - d] |= s * 128;
};
